/**
 * 非必要 请勿修改
 */

function isRegExp(v) {
  return _toString.call(v) === '[object RegExp]'
}
/**
 * Remove an item from an array.
 */
function remove(arr, item) {
  if (arr.length) {
    const index = arr.indexOf(item)
    if (index > -1) {
      return arr.splice(index, 1)
    }
  }
}
function isDef(v) {
  return v !== undefined && v !== null
}
function isAsyncPlaceholder(node) {
  return node.isComment && node.asyncFactory
}
function getFirstComponentChild(children) {
  if (Array.isArray(children)) {
    for (let i = 0; i < children.length; i++) {
      const c = children[i]
      if (isDef(c) && (isDef(c.componentOptions) || isAsyncPlaceholder(c))) {
        return c
      }
    }
  }
}
function getComponentName(opts) {
  return opts && (opts.Ctor.options.name || opts.tag)
}

function getRoutePath() {
  return this.$route.path
}

function matches(pattern, name) {
  if (Array.isArray(pattern)) {
    return pattern.indexOf(name) > -1
  } else if (typeof pattern === 'string') {
    return pattern.split(',').indexOf(name) > -1
  } else if (isRegExp(pattern)) {
    return pattern.test(name)
  }
  /* istanbul ignore next */
  return false
}
function pruneCache(keepAliveInstance, filter) {
  const { cache, keys, _vnode } = keepAliveInstance
  for (const key in cache) {
    const entry = cache[key]
    if (entry) {
      const name = entry.name
      if (name && !filter(name)) {
        pruneCacheEntry(cache, key, keys, _vnode)
      }
    }
  }
}
function pruneCacheEntry(cache, key, keys, current) {
  const entry = cache[key]
  if (entry && (!current || entry.name !== current.name)) {
    entry.componentInstance.$destroy()
  }
  cache[key] = null
  remove(keys, key)
}
const patternTypes = [String, RegExp, Array]
export default {
  name: 'keep-alive',
  abstract: true,
  props: {
    include: patternTypes,
    exclude: patternTypes,
    max: [String, Number]
  },

  data() {
    return {
      // cache: {},
      // keys: [],
      // vnodeToCache: undefined,
      // keyToCache: undefined,
    }
  },

  methods: {
    cacheVNode() {
      const { cache, keys, vnodeToCache, keyToCache } = this
      if (vnodeToCache) {
        const { tag, componentInstance, componentOptions } = vnodeToCache
        cache[keyToCache] = {
          name: getRoutePath.call(this),
          tag,
          componentInstance,
          cid: componentOptions.Ctor.cid
        }
        keys.push(keyToCache)
        // prune oldest entry
        if (this.max && keys.length > parseInt(this.max)) {
          pruneCacheEntry(cache, keys[0], keys, this._vnode)
        }
        this.vnodeToCache = null
      }
    }
  },
  created() {
    this.cache = Object.create(null)
    this.keys = []
  },
  destroyed() {
    for (const key in this.cache) {
      pruneCacheEntry(this.cache, key, this.keys)
    }
  },
  mounted() {
    this.cacheVNode()
    this.$watch('include', val => {
      pruneCache(this, name => matches(val, name))
    })
    this.$watch('exclude', val => {
      pruneCache(this, name => !matches(val, name))
    })
  },
  updated() {
    this.cacheVNode()
    // console.log(this.cache,this.keys);
  },
  render() {
    const slot = this.$slots.default
    const vnode = getFirstComponentChild(slot)
    const componentOptions = vnode && vnode.componentOptions
    if (componentOptions) {
      // check pattern
      const name = getRoutePath.call(this)
      const { include, exclude } = this
      if (
        // not included
        (include && (!name || !matches(include, name))) ||
        // excluded
        (exclude && name && matches(exclude, name))
      ) {
        return vnode
      }
      const { cache, keys } = this
      const key =
        vnode.key == null
          ? // same constructor may get registered as different local components
            // so cid alone is not enough (#3269)
            componentOptions.Ctor.cid + (componentOptions.tag ? `::${componentOptions.tag}` : '')
          : vnode.key
      if (cache[key]) {
        //判断cid是否相同, 不同则有过热重载的reload, 需要重建缓存
        if (vnode.componentOptions.Ctor.cid === cache[key].cid) {
          vnode.componentInstance = cache[key].componentInstance
          // make current key freshest
          remove(keys, key)
          keys.push(key)
        } else {
          cache[key].componentInstance.$destroy()
          cache[key] = vnode
        }
      } else {
        // delay setting the cache until update
        this.vnodeToCache = vnode
        this.keyToCache = key
      }
      vnode.data.keepAlive = true
    }
    return vnode || (slot && slot[0])
  }
}
